Link towards .html files

[paugier]

Describe the bug

context

When I have a .html file pres.slide.html in a directory my-great-presentation next to a markdown file, I try to create a link with [my great presentation](./my-great-presentation/pres.slide.html).

expectation

I expect the html file to be included in the website and a link to be created towards this file.

bug But instead I get the following error message:

$ jupyter-book build mybook
WARNING: 'myst' reference target not found: ...

Currently, the workaround is to use html_extra_path and to write the link in html.

Reproduce the bug

I hope it is already described...

List your environment

jupyter-book --version
Jupyter Book      : 0.13.1
External ToC      : 0.2.4
MyST-Parser       : 0.15.2
MyST-NB           : 0.13.2
Sphinx Book Theme : 0.3.3
Jupyter-Cache     : 0.4.3
NbClient          : 0.5.13

[welcome[bot]]

Thanks for opening your first issue here! Engagement like this is essential for open source projects! :hugs:
If you haven't done so already, check out EBP's Code of Conduct. Also, please try to follow the issue template as it helps other community members to contribute more effectively.
If your issue is a feature request, others may react to it, to raise its prominence (see Feature Voting).
Welcome to the EBP community! :tada:

[paugier]

Kind of related to #1113 (but actually different).

[saulshanabrook]

I was able to get this working by embedding rst in the page, like this:

    ```{eval-rst}
    `Presentation as HTML <../pldi_2023_presentation.slides.html>`_
    ```